We will continue work on cytoplasmic actin, myosin and associated proteins using both biochemical and morphological methods to study their relation to cellular movements. We will use labeled antibodies at the light and electron microscope levels to localize the major contractile proteins during cell division, cell locomotion, platelet activation and other cell movements. As a model system for the analysis of interactions of contractile proteins with membranes, we will localize myosin, alpha-actin and tropomyosin in the isolated intestinal brush border and attempt to isolate the molecule (s) which bind actin to the membrane. We will continue biochemical work on Acanthamoeba contractile proteins: (1) We will study the relationship of the 2 classes of Acanthamoeba myosin to each other using immunochemical methods. These antibodies will also be used to localize the myosins inside the amoeba and for microinjection experiments designed to learn which movements require each myosin type. (2) We will fractionate amoeba extracts to purify the various gelation factors which can cross-link actin to form a gel. The purified gelation factors will be characterized and used to develop assays to identify and isolate the proteins which regulate gel formation.